CDKs (cyclin-dependent kinases) are cell growth control factors that are involved in entry to DNA synthesis (S phase) of the cell cycle and a mitotic phase (M phase), etc., and many types of CDKs are known. Also, the activation of CDK is controlled in multiple stages through the phosphorylation or dephosphorylation of the threonine residue of active loop (T loop) in its three-dimensional structure. When the particular threonine residue of CDK is phosphorylated, it forms a complex with a particular cyclin and is activated. This complex, which is important for cell cycle control, includes CDK1, CDK2/cyclin A, CDK1/cyclins B1 to B3 and CDK2, CDK4, CDK5, CDK6/cyclin D1 to D3, and CDK2/cyclin E, which are respectively involved in the particular periods of the cell cycle. CDK7 forms a CDK-activating kinase (CAK) together with cyclin H and MAT1 in metazoans and participates in the phosphorylation of CDKs (e.g., CDK1, CDK2, CDK4, and CDK6) necessary for the progression of the cell cycle (see Non Patent Literature 1).
Cell overgrowth by the abnormal activation of CDKs is a common feature in many cancers, and it is known that this is associated with a loss of checkpoint functions involved in the cell cycle control of cancer cells (see Non Patent Literature 2). Also, CDKs are known to have functions other than cell cycle control, and CDK7 is known to promote the binding of RNA polymerase II (RNAPII) to DNA and elongation thereof to positively control the transcription through the phosphorylation of serine in the COOH-terminal domain of the RNAPII (see Non Patent Literature 3).
CDK7 inhibitors exhibit effects in cell growth tests of various cancer cells and cancer-bearing mouse models, and the inhibition is expected to be useful as anticancer agents (see Non Patent Literatures 4 and 5).
Furthermore, it has been reported that in collagen-induced rheumatism mouse models, amelioration of clinical scores or tissue damage, decrease in the levels of inflammation-induced cytokines such as IL-6, IL-1β, and IL-17, and anti-CII-IgG2α, and decrease in the proportion of Th17 cells are attained by inhibiting CDK7 (see Non Patent Literature 6).
The CDK7 inhibitors, which play an important role in the progression of the cell cycle, are further expected to also have effects on the suppression of infection by viruses such as HIV, EBV, and HCV, and cardiomegaly (see Non Patent Literatures 7 and 8). Examples of diseases for which the CDK7 inhibitors seem to be useful, in addition to those described above, include autoimmune diseases typified by psoriasis and multiple sclerosis, neurodegenerative diseases typified by Alzheimer's disease, etc., allergic diseases typified by atopic dermatitis, etc., chronic respiratory diseases typified by chronic obstructive pulmonary disease (COPD), etc., and fibrosis typified by idiopathic pulmonary fibrosis, etc. (see Non Patent Literatures 9 to 11 and Non Patent Literatures 16 to 18).
Although the development of many CDK inhibitors is currently underway, there are not many compounds having an excellent CDK7 inhibitory effect (see Non Patent Literature 15).